A wake-up radio can be used in devices, such as IEEE 802.11 devices, to save power. For example, a device can include a wake-up radio as well as a primary radio. The wake-up radio can be a simple receiver without any transmission functionality, and the primary radio can have both transmitting and receiving functionalities. The wake-up radio can be active while the primary radio is off. Typically, if the device has no data to transmit or receive, the primary radio is off and the wake-up radio is active. When the access point has a data packet buffered for the device, the access point can transmit a wake-up trigger frame to the device. The wake-up radio can receive the wake-up trigger frame and the device can decide whether to wake up the primary radio to receive the packet. The wake-up radio typically has a low power consumption, for example, less than 100 microwatts in the active state. By using the wake-up radio, the device can reduce the power consumption. Low power consumption can be important for battery-powered devices, such as wearable devices.
Like reference numbers and designations in the various drawings indicate like elements.